One of the many challenges in performing an oil well cementing operation may include accurately measuring the level of a cement slurry in a tub during some part of the mixing and pumping process. A number of different measurement techniques have been proposed for this purpose, including contact probe based techniques such as torque tubes, RF capacitance, guided wave and line powered radar. Each of these techniques has specific drawbacks, but universally such probes have a fundamental problem that they must actually be in contact with the cement slurry in order to measure the level of the slurry in the mix tub. These contact based techniques subject the probe to cement build-up which eventually results in a degradation in sensor performance associated with the build-up.
In response to this fundamental deficiency, a number of non-contact measurement techniques have been utilized, including ultrasonic transmission. However, ultrasonic non-contact sensors are functionally unreliable in some applications. For example, in cementing applications, ultrasonic non-contact sensors are unreliable in distinguishing between a cement slurry and a foam that often forms on the surface of the slurry during the mixing thereof. Accordingly, a new technique capable of measuring the level of a fluid in a container without contacting the fluid is desired.